Mechanical refrigeration systems, and related heat transfer devices such as heat pumps and air conditioners, using refrigerant liquids are well known in the art for industrial, commercial and domestic uses. Chlorofluorocarbons (CFCs) were developed in the 1930s as refrigerants for such systems. However, since the 1980s the effect of CFCs on the stratospheric ozone layer has become the focus of much attention. In 1987 a number of governments signed the Montreal Protocol to protect the global environment setting forth a timetable for phasing out the CFC products. CFC's were replaced with more environmentally acceptable materials that contain hydrogen or hydrochlorofluorocarbons (HCFC's). Subsequent amendments to the Montreal protocol accelerated the phase-out of these CFCs and also scheduled the phase-out of HCFCs. Additionally, it is expected that the European Union member states will shortly recommend banning the use of materials that have a Global Warming Potential (GWP) of 50 or more. Thus, there is a requirement for a non-flammable, non-toxic alternative to replace these CFCs and HCFCs. In response to such demand industry has developed a number of hydrofluorocarbons (HFCs), which have a zero or near zero ozone depletion potential.
CF3I is a non-toxic, non-flammable, low global warming potential molecule with almost zero ozone depletion potential. Also the life cycle of the CF3I in the atmosphere is only a couple of days. Thus, there is incentive to synthesize this molecule in a low-cost route for using it as a refrigerant with or without the presence of a known or existing refrigerants. The CF3I is also useful a foam blowing agent and can be used to replace more environmentally damaging foam blowing agent previously employed in the production of polymeric foams.
Prior to this invention the methods known for the production of CF3I have involved or required one or more of expensive and/or not readily available reactants, multi-steps processes, processes with low selectivity for CF3I, processes with low yields, and processes limited to lab scale production quantities. The following are exemplary of such prior art processes.
In the article “Study on a novel catalytic reaction and its mechanism for CF3I synthesis”, Nagasaki, Noritaka et al., Catalysis Today (2004), 88(3–4), 121–126, a vapor phase production process has synthesized CF3I by the reaction between CHF3 with I2 in the presence of a catalyst including alkali metal salts, which are supported on an activated carbon carrier. A consideration of the reaction mechanism suggests that the reaction proceeds via CF2 carbenes formed on the catalyst surface as intermediates, followed by carbene disproportionation to CF3 radicals, followed by reaction with I2 to give CF3I.
It has been claimed in JP 52068110 that CF3I is prepared in high yield by vapor-phase reaction of Freon 23 with iodine in the presence of alkali or alkaline earth metal salts. Thus, 200 mL/min Freon 23 is introduced to iodine, the resulting gaseous mixture of Freon 23 and iodine (iodine/Freon=2.2 molar) is passed over 800 mL active carbon containing 7.5% KF for 10 h at 500° C. to give 57.8% CF3I.
In DE 1805457 CF3I and C2F5I have been prepared from the corresponding bromides and KI without solvents. Thus, 0.3 mole CF3Br are passed through a layer of 3 mole KI of 6–8 micron particle size at 500° C. to give 15% CF3I, 0.3% C2F6, and 85% CF3Br, which is then recycled.
CF3Br have also been used as a starting material to synthesize CF3I in a multi-step reaction protocol in “Preparation and properties of ZnBr(CF3) 2 L—a convenient route for the preparation of CF3I”, Naumann, Dieter; et al, Journal of Fluorine Chemistry (1994), 67(1), 91–3. ZnBr(CF3) 2 L (L=DMF, MeCN) is prepared by the reactions of CF3Br with elemental Zn in better than 60% yield. The reaction of ZnBr(CF3)2DMF with Iodine monochloride in DMF solution yields pure CF3I in better than 70% yield.
In a similar approach, disclosed in EP 266821 and U.S. Pat. No. 4,794,200, CF3I is prepared from CF3Br by contact with a metal or an alkali metal dithionite and SO2 in solution followed by filtration and treatment with iodine in a carboxylic or sulfonic acid. Thus, Zn, NaOH, and SO2 in DMF in a Parr app. were pressurized with 3.7 bar CF3Br and the mixture. stirred 2 h whereupon the product was heated at 120° C. over 9 h with iodine in HOAc during which CF3I (32%) was generated and recovered.
A direct synthesis of CF3I by direct iodination of CF3CO2H with iodine has been claimed using a flow reactor over various salt-impregnated catalysts, such as copper iodide on activated carbon, in “Synthesis of CF3I by direct iodination of CF3COOH on solid catalyst”, Lee, Kyong-Hwan et al, Hwahak Konghak (2001), 39(2), 144–149. In this experiment, the effects of support types, salt types and salt contents for the manufactured catalysts and also those of reaction conditions such as reaction temperature, contact time and feeding mole ratio of reactant are tested. It has been reported that a longer contact time led to the higher yield of CF3I. The optimized reaction conditions were above 1 of I2/CF3COOH mole ratio and about 400° C. of reaction temp. Active-carbon as a support shows better performance than alumina. For the salt impregnated on support, the best results of both salt content and salt type are 7.5 wt. percentages and CuI type, respectively. In the reaction conditions in this article, the catalyst was readily deactivated.
In “A simple, novel method for the preparation of trifluoromethyl iodide and diiododifluoromethane”, Su, Debao et al., Journal of the Chemical Society, Chemical Communications (1992), (11), 807–8, CF3I has been synthesized in 70–80% yields by treatment of XCF2CO2Me (X=Cl or Br) with iodine in the presence of potassium fluoride and copper (I) iodide. If KI is used instead of KF under similar conditions, CF2I2 is obtained in 50–60% yields with traces of MeI present. Reaction of BrCF2CO2K with KI and I2 in the presence of CuI gave CF2I2 in 50–60% yield without traces of MeI.
In a different approach, in “Synthesis and purification of iodotrifluoromethane, bromotrifluoromethane, trifluoromethane-d1 for laser isotope separation”. Chiriac, Maria et al., Revistade Chimie (Bucharest, Romania) (1982), 33(11), 1018–20, CF3I of 99.9% purity have been prepared with yield >80% from Ag-trifluoroacetate.
There is, therefore, a need for an alternative, fairly simple and inexpensive process, and preferably a one-step process, for the production of CF3I that does not require expensive and/or not readily available reactants, and in which the process can be commercially adapted.